Npflex

To visualize the instability patterns distributed on the gel surfaces, we used an Olympus IX73 fluorescent microscope (Tokyo, Japan). The microscope can also work as an interferometer with a monochromatic filter (532/25 nm VIS Band Pass Filter) (Optolong Optics CO., Ltd., Kunming, China). To analyze the 3D morphology of the instabilities, we further carried out white-light interferometric measurements by using a surface profiler (Bruker NPFLEX, Billerica, MA, USA). The instrument could precisely reconstruct the 3D surface profiles and measure the average roughness and maximum vertical deformations of the substrates.

A White Light Interferometer (WLI) (Bruker NPFlex) was used to measure the surface roughness of the COC moulds and lenses. The WLI was performed in Vertical Scanning Interferometry (VSI) mode, all images were then processed in Vision 64 with either a Terms removal-F operator and Stylus analysis (7 lengths) filer, or Gaussian regression filter and S (roughness) height parameters calculation. The filters removed any curvature of the moulds and lenses to obtain a flat surface for roughness calculation. The contact lenses required care and attention when measuring. Lenses were cut into smaller pieces using a clean scalpel to mitigate curvature. To mitigate the impact of surface debris on the measurements, the lenses were cleaned in an IPA/DI water mix under ultrasonication, then placed back into DI water overnight before measurement. Excess water was removed and the lens placed on a clean glass slide. Measurements were performed several times. If excess water remained on the surface, the roughness value was unrealistic (below that of the mould). Conversely, if the lens dehydrated excessively the surface roughness value was much greater than the mould. Dehydration was clear when the lens was visibly curling off the surface of the slide. Typically, lens measurements were strictly required to be completed within several minutes of removal from the storage vial.